Fair Value Measurements (Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	$ 94,023	$ 77,478	$ 53,591
Specific valuation allowance allocations	(9,186)	(4,378)	(1,680)
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	0	0	0
Specific valuation allowance allocations	0	0	0
Fair value	0	0	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	33,626	14,921	2,715
Specific valuation allowance allocations	(3,961)	(2,765)	(1,475)
Fair value	$ 29,665	$ 12,156	$ 1,240